Light-Emitting Element With Gradient Band Gap Active Layer
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Solution Overview
Problem
Light emitting elements with a multi-quantum well structure experience reduced light emission efficiency due to stress and polarization in the active layer caused by lattice constant differences between quantum barrier and well layers, leading to inefficient electron and hole recombination.
Innovation Solution
A light emitting element with an active layer having alternately laminated barrier and well layers, where the energy band gap varies linearly, with first regions between barrier and well layers having a decreasing band gap and second regions having an increasing band gap, and differing thicknesses and In content gradients, along with an electron blocking layer to enhance injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multi-quantum well structure with alternately laminated barrier and well layers is used, then light emission function is enabled, but stress and polarization occur due to lattice constant difference, reducing light emission efficiency
Solution Approach 1:
The patent applies parameter changes by introducing linearly varying band gap regions between the barrier layers and well layers. The band gap is linearly decreased in first regions and linearly increased in second regions, creating a gradient structure that gradually transitions between materials with different lattice constants. This gradual transition reduces stress and polarization effects while maintaining the light emission function of the quantum well structure.
Solution Approach 2:
The patent employs composite materials by creating a complex multi-layer structure comprising barrier layers, well layers, and intermediate regions with linearly varying band gaps. This composite structure combines materials with different properties (different band gaps and lattice constants) in a controlled sequence, where the intermediate regions act as transition zones that mitigate the harmful effects of direct material interfaces.
2Reliability
If polarization occurs in the active layer, then energy band bending occurs, but electron and hole distribution becomes inclined toward opposite layers, reducing recombination efficiency
Solution Approach 1:
The patent changes the energy band parameter by introducing regions with linearly varying band gaps between the barrier and well layers. This gradual band gap transition modifies the energy landscape, reducing abrupt band bending caused by polarization. The linearly decreased and increased band gap regions create a more favorable energy distribution that promotes balanced electron and hole injection into the well layers, thereby improving recombination efficiency.
3Use of energy by moving object
If uniform thickness is used for all layers in the active layer, then manufacturing is simplified, but stress relief and light emission efficiency are compromised
Solution Approach 1:
The patent applies local quality by assigning different thicknesses to different regions within the active layer. Specifically, the first regions (with linearly decreasing band gap) and second regions (with linearly increasing band gap) have different thicknesses, allowing each region to be optimized for its specific function: stress relief, band gap transition, or light emission. This localized optimization improves overall light emission efficiency while managing the complexity through a systematic thickness variation pattern.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution relieves stress in the active layer, improves electron and hole injection efficiency, and enhances light emission efficiency by adjusting the energy band gap and In content gradients, reducing polarization and increasing recombination efficiency.
Implementation Method 1
Light emitting elements, such as light emitting diodes (LEDs) and laser diodes, which use a Group III-V or Group II-VI compound semiconductor material
Implementation Method 2
the energy band gap is linearly decreased in first regions disposed between adjacent ones of the barrier layers and the well layers and linearly increased in second regions disposed between adjacent ones of the well layers and the barrier layers
Data Source
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AI summary
According to one embodiment, a light-emitting element comprises: a first electrically-conductive semiconductor layer, a second electrically-conductive semiconductor layer; and an active layer which is disposed between the first electrically-conductive layer and the second electrically-conductive layer, and in which a well layer and a barrier layer are alternately laminated at least once. The active layer comprises: a first region which is disposed between a neighbouring barrier layer and well layer, and linearly reduces the energy band gap; and a second region which is disposed between a neighbouring well layer and barrier layer, and linearly increases the energy band gap. In the well layer, at least one first region and second region neighbouring the same well layer have mutually different thicknesses.